A frequency converter busbar short-circuit protection device and protection method

Abstract

The present invention provides a frequency converter busbar short-circuit protection device and protection method, including a busbar short-circuit detection module, a shunt release, and a circuit breaker arranged in the frequency converter; by adding a capacitor voltage sampling circuit to the energy storage filter unit configured in a conventional frequency converter, it is detected whether the capacitor voltage is lower than a set value, and the control circuit determines whether a busbar short circuit occurs based on the sampled voltage and makes a judgment in the shortest possible time whether to send a disconnection signal, thereby realizing a rapid protection function for a short-circuit condition of the laminated busbar. The present invention detects a short-circuit fault through voltage at the very beginning of the short circuit, and the short-circuit current does not rise to a large value, thereby avoiding the consequences of large-scale burning caused by the short circuit. The present invention realizes the protection function only through a simple circuit, does not require the addition of a complex module, and does not require the replacement of components when restoring the original state after a short circuit, thereby reducing manufacturing and maintenance costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of short-circuit detection and protection, and in particular relates to a frequency converter busbar short-circuit protection device and a protection method. Background Art

[0002] Frequency converters used in variable frequency speed regulation typically consist of various modules, including a rectifier, power-up buffer, filter and energy storage modules, inverter, control, and drive modules. Analysis of multiple field damage cases reveals that when internal components in these modules, such as the rectifier, power-up buffer, inverter, control, and drive modules, fail, damage is localized within the module itself and does not affect adjacent modules. However, if a short circuit occurs in the filter and energy storage module, the corresponding rectifier, power-up buffer, and inverter modules will all be fatally damaged, necessitating replacement of the entire inverter. Therefore, a short circuit in the filter and energy storage module is the most severe, resulting in the greatest losses.

[0003] The filter energy storage module is a centralized unit for energy and high voltage, primarily consisting of a busbar, electrolytic capacitors, and equalizing resistors. The electrolytic capacitors and equalizing resistors are designed with a large safety distance and space to prevent short circuits. Furthermore, the electrolytic capacitors and equalizing resistors are reinforced with insulation in places other than the wiring terminals, preventing them from short-circuiting during production, transportation, or harsh environments. The busbar is different. Due to the peak voltage requirement of the IGBT (Insulated Gate Bipolar Transistor) when it is turned off, the parasitic inductance of the busbar must be as small as possible. The only way to reduce parasitic inductance is to use a laminated busbar structure. Figure 3 This laminated structural design results in very small safety distances between the busbar's internal wires. The positive, neutral, and negative wires are completely isolated by insulating paper. During production, transportation, wiring, and maintenance, the insulating paper can be cut, scratched, or cracked. Once damaged, the insulation fails, causing a short circuit. Therefore, the greatest risk of a short circuit in the filter and energy storage module lies in the laminated busbar. Therefore, how to quickly protect the inverter against a laminated busbar short circuit has become a key research topic.

[0004] In the case of busbar short circuit, the following methods are generally used for protection:

[0005] 1. Method of disconnecting the distribution circuit breaker due to overcurrent. Existing general-purpose inverters generally do not have special circuits or protection logic designed for busbar short circuits. When a busbar short circuit occurs, it can only rely on the instantaneous overcurrent protection of the user-configured distribution circuit breaker. This method has obvious defects: the current is not large in the initial stage of the busbar short circuit. Only after a certain period of time, when the short circuit becomes more and more serious, will the short-circuit current be reached to cause the circuit breaker to trip. This time is more than 400 milliseconds. The instantaneous protection value of the circuit breaker reaches 8 times the rated current. When the input current value reaches 8 times the protection value of the circuit breaker, the electrolytic capacitors, rectifier bridges, etc. in the inverter are completely damaged. The high-voltage arc that may be generated during the short circuit will damage the IGBT. Therefore, the circuit breaker protection method can only protect against fire, personal safety, etc., and cannot protect the inverter's own components.

[0006] 2. A method of judging whether there is a capacitor short circuit by the saturation characteristics of the IGBT. For example, in the patent with patent number CN102957133A, an IGBT with overcurrent protection is connected in series on the negative busbar, and the saturation characteristics of the IGBT are used to judge whether the busbar is overcurrent. The advantages of this method are fast response speed, reasonable and accurate overcurrent protection value, and far superior to the aforementioned method of overcurrent through a circuit breaker. However, the disadvantages of this method are very obvious: the added IGBT for overcurrent protection is very expensive, and the driver, heat dissipation system, connecting copper busbar, etc. that work with this IGBT will add additional cost to the system, and the corresponding volume will also increase; on the other hand, this method can effectively protect the capacitor short circuit problem that occurs during the operation of the machine, but if a short circuit occurs inside the capacitor when the machine is in standby mode, even if the capacitor itself starts to burn, the current flowing through the busbar is not large, and this method cannot provide protection.

[0007] 3. Connect fuses directly in series with the busbars. This method protects the capacitors by disconnecting the fuses when a short circuit occurs. This method offers fast response and requires no software input for judgment and control. However, this method has significant drawbacks: the fuses and connecting busbars add additional system costs, and after disconnecting, the fuses must be replaced for normal operation, increasing maintenance costs. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a converter busbar short-circuit protection device and protection method for realizing a rapid protection function for a laminated busbar short-circuit condition.

[0009] The technical solution adopted by the present invention to solve the above technical problems is as follows: a busbar short-circuit protection device for a frequency converter, comprising a busbar short-circuit detection module, a shunt release and a circuit breaker arranged in the frequency converter; the frequency converter comprises a rectifier module, a power-on buffer module, an energy storage filter module and an inverter module connected in series in sequence, the busbar short-circuit detection module is connected in parallel between the positive and negative ends of the DC bus of the energy storage filter module through a detection input end, and is used to detect the voltage between the positive and negative ends of the DC bus and determine whether a short circuit occurs The busbar short circuit detection module is connected to the signal input terminal of the shunt release KT1 and the contactor KM1 of the power-on buffer module through the signal output terminal, respectively, for sending a disconnection signal; the shunt release KT1 is connected to the circuit breaker through the transmission mechanism, for disconnecting the circuit breaker when receiving the disconnection signal; the circuit breaker includes an incoming circuit breaker QF1 and a second circuit breaker QF2, or the circuit breaker includes an incoming circuit breaker QF1; the contacts of the incoming circuit breaker QF1 are connected in series in the incoming three-phase AC power main circuit of the inverter, and the first The contacts of the second circuit breaker QF2 are connected in series in the DC bus circuit of the inverter, and are used to disconnect the current flowing through the DC bus of the inverter by opening the circuit breaker contacts. The contactor KM1 is connected in parallel across the power-on buffer resistor R1, and is used to close the contacts to bypass the power-on buffer resistor R1 when power-on charging is completed, and to open the contacts upon receiving a disconnect signal, thereby disconnecting the current flowing through the DC bus of the inverter. The bus short-circuit detection module includes a first sampling circuit M1, a second sampling circuit M2, and a control circuit. The detection input terminals of the first sampling circuit M1 and the second sampling circuit M2 are respectively connected in parallel across the first series capacitor C1 and the second series capacitor C2 of the energy storage filter module of the inverter. The signal output terminals of the first sampling circuit M1 and the second sampling circuit M2 are respectively connected to the signal input terminal of the control circuit, and are used to sample the voltage across the energy storage filter capacitor, convert it into a low-voltage analog signal, and send it to the control circuit. The control circuit is used to preset the short-circuit threshold voltage and short-circuit threshold time, determine the short-circuit status, and send a disconnect signal.

[0010] According to the above scheme, the second circuit breaker QF2 and the power-on buffer resistor R1 are connected in series in sequence to the positive end of the DC bus of the inverter's power-on buffer module. The shunt release KT1 is connected to the second circuit breaker QF2 through a transmission mechanism and is configured to receive the protection signal PC sent by the bus short-circuit detection module and disconnect the second circuit breaker QF2, thereby interrupting the current flowing through the power-on buffer resistor R1. The contacts of the contactor KM1 are connected in parallel across the series circuit of the second circuit breaker QF2 and the power-on buffer resistor R1. The contactor KM1 is configured to receive the contactor signal CC sent by the bus short-circuit detection module and disconnect the contacts of the contactor KM1.

[0011] According to the above scheme, the incoming circuit breaker QF1 includes three switches that are connected in series on the three-phase input power lines L1, L2, and L3 of the inverter, and are linked to each other for on and off. The shunt release KT1 is connected to the incoming circuit breaker QF1 through a transmission mechanism. The shunt release KT1 is used to receive the protection signal PC sent by the bus short-circuit detection module, disconnect the incoming circuit breaker QF1, thereby disconnecting the three-phase input power of the inverter, and finally disconnecting the current flowing through the DC bus of the inverter.

[0012] A method for protecting a frequency converter busbar from short circuit includes the following steps:

[0013] S1: Preset short-circuit threshold voltage U in the control circuit of the busbar short-circuit detection module S and short-circuit threshold time T S ;

[0014] S2: The first sampling circuit M1 detects the first series capacitor C1 to obtain the voltage U C1 , converts it into an analog signal U1 and sends it to the control circuit; the second sampling circuit M2 detects the second series capacitor C2 to obtain the voltage U C2 , converts it into an analog signal U2 and sends it to the control circuit; the control circuit records the duration T of the voltage;

[0015] S3: The control circuit determines whether a short circuit occurs. If no short circuit occurs, step S2 is executed; if a short circuit occurs, a disconnection signal is sent to enable the protection device to complete the corresponding action and step S4 is executed;

[0016] S4: The control circuit determines whether the short-circuit fault is eliminated; if the short-circuit fault is not eliminated, the disconnection signal is continuously issued; if the short-circuit fault is eliminated, the disconnection signal is stopped and step S2 is executed.

[0017] Furthermore, if the shunt release KT1 is connected to the second circuit breaker QF2, the specific steps in step S3 are as follows:

[0018] The control circuit compares the voltage U1, voltage U2 and the short-circuit voltage threshold U S The value of the short circuit time threshold T and the duration T S Size:

[0019] If U1>U S 、U2>U S , and T>T S , determine that no short circuit occurs, mark the short circuit state as A, and execute step S2;

[0020] If U1<U S 、U2>U S , and T>T S, it is determined that the first series capacitor C1 is short-circuited, the short-circuit state is marked as B, the control circuit sends a protection signal PC to disconnect the shunt release KT1 to disconnect the second circuit breaker QF2, and sends a contactor signal CC to disconnect the contacts of the contactor KM1, and prompts the user that the first series capacitor C1 is short-circuited;

[0021] If U1>U S 、U2<U S , and T>T S , determine that the second series capacitor C2 is short-circuited, mark the short-circuit state as C, and the control circuit sends a protection signal PC to disconnect the shunt release KT1 to disconnect the second circuit breaker QF2, and sends a contactor signal CC to disconnect the contacts of the contactor KM1, and prompt the user that the second series capacitor C2 is short-circuited;

[0022] If U1<U S 、U2<U S , and T>T S , it is determined that the busbar is directly short-circuited, and the short-circuit state is marked as D. The control circuit sends a protection signal PC to disconnect the shunt release KT1 and disconnect the second circuit breaker QF2, and sends a contactor signal CC to disconnect the contacts of the contactor KM1, and prompts the user that the busbar is short-circuited.

[0023] Furthermore, if the shunt release KT1 is connected to the incoming circuit breaker QF1, the specific steps in step S3 are as follows:

[0024] The control circuit compares the voltage U1, voltage U2 and the short-circuit voltage threshold U S The value of the short circuit time threshold T and the duration T S Size:

[0025] If U1>U S 、U2>U S , and T>T S , determine that no short circuit occurs, mark the short circuit state as A, and execute step S2;

[0026] If U1<U S 、U2>U S , and T>T S , it is determined that the first series capacitor C1 is short-circuited, the short-circuit state is marked as B, the control circuit sends a protection signal PC to disconnect the shunt release KT1 and disconnect the incoming circuit breaker QF1, and prompt the user that the first series capacitor C1 is short-circuited;

[0027] If U1>U S 、U2<U S , and T>T S, it is determined that the second series capacitor C2 is short-circuited, the short-circuit state is marked as C, the control circuit sends a protection signal PC to disconnect the shunt release KT1 and disconnect the incoming circuit breaker QF1, and prompt the user that the second series capacitor C2 is short-circuited;

[0028] If U1<U S 、U2<U S , and T>T S , it is determined that the busbar is directly short-circuited, the short-circuit state is marked as D, the control circuit sends a protection signal PC to disconnect the shunt release KT1 and disconnect the incoming circuit breaker QF1, and prompt the user that the busbar is short-circuited.

[0029] The beneficial effects of the present invention are:

[0030] 1. The inverter busbar short-circuit protection device of the present invention adds a capacitor voltage sampling circuit to the energy storage filter unit configured in a conventional inverter to detect whether the capacitor voltage is lower than a set value. The control circuit determines whether a busbar short-circuit occurs based on the sampled voltage and determines whether to send a disconnect signal in the shortest possible time, thereby achieving a rapid protection function for short-circuit conditions of the laminated busbar.

[0031] 2. The present invention detects the short-circuit fault through voltage at the initial stage of the short circuit and responds within 1 to 10 milliseconds. During this period, the short-circuit current does not rise to a large value, and will not cause serious damage to other components inside the inverter, thus avoiding the adverse effect of large-area burning caused by the short circuit.

[0032] 3. The present invention realizes the protection function only through a simple circuit, does not need to add a complex module, and does not need to replace the device when restoring the original state after a short circuit, thereby reducing the manufacturing and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 1 is a circuit diagram of embodiment 1 of the present invention.

[0034] Figure 2 This is a circuit diagram of embodiment 2 of the present invention.

[0035] Figure 3 1. It is a diagram showing the internal composition and overall formation of the laminated busbar according to an embodiment of the present invention.

[0036] Figure 4 is a flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] The inverter includes a rectifier module, a power-up buffer module, an energy storage filter module, and an inverter module, all connected in series. The circuit breaker comprises an incoming line breaker QF1 and a second circuit breaker QF2. The incoming line breaker QF1 includes three switches, connected in series to the inverter's three-phase input power lines L1, L2, and L3, for connecting, carrying, and disconnecting the three-phase AC power supply under normal and abnormal circuit conditions. The rectifier module comprises a three-phase diode bridge rectifier consisting of six diodes (D1 to D6) to convert the incoming three-phase AC power into DC power. The power-up buffer module includes a parallel-connected power-up buffer resistor R1 and a contactor KM1. The power-up buffer resistor R1 is used to buffer the inrush current in the DC circuit during power-up and to charge the capacitor of the energy storage filter module. The contacts of contactor KM1 are normally open and close after power-up, bypassing the power-up buffer resistor R1. The energy storage filter module includes a first series capacitor C1 and a second series capacitor C2, as well as a first and a second voltage equalizing resistor R2 and R3 connected in parallel across the first and second series capacitors C1 and C2, respectively. The energy storage filter module is connected in parallel between the positive and negative terminals of the DC bus and is used to smooth and filter the rectified DC power. The inverter module includes a three-phase inverter bridge consisting of six IGBTs (Q1 to Q6) to convert the DC voltage into an equivalent AC voltage output.

[0039] See also Figure 1In Example 1 of the present invention, a busbar short-circuit detection module is connected in parallel between the positive and negative terminals of the DC busbar of the energy storage filter module via a detection input terminal, and is used to detect the voltage between the positive and negative terminals of the DC busbar and determine whether a short circuit has occurred. The busbar short-circuit detection module includes a first sampling circuit M1, a second sampling circuit M2, and a control circuit; the detection input terminals of the first sampling circuit M1 and the second sampling circuit M2 are respectively connected in parallel to the first series capacitor C1 and the second series capacitor C2 of the energy storage filter module of the inverter; the signal output terminals of the first sampling circuit M1 and the second sampling circuit M2 are respectively connected to the signal input terminal of the control circuit, and are used to sample the voltage across the energy storage filter capacitor, convert it into a low-voltage analog signal, and send it to the control circuit. The control circuit is used to preset a short-circuit threshold voltage and short-circuit threshold time, determine the short-circuit state, and send a disconnection signal. The busbar short-circuit detection module is connected to the signal input terminals of the shunt release KT1 and contactor KM1 through its signal output terminal. The shunt release KT1 is connected to the second circuit breaker QF2 through a transmission mechanism. The second circuit breaker QF2 is a miniature circuit breaker with normally closed contacts. It can be closed and opened manually or opened by the control circuit through the shunt release KT1. The second circuit breaker QF2 and the power-on buffer resistor R1 are connected in series with the positive terminal of the DC bus of the inverter's power-on buffer module. The shunt release KT1 is used to receive the protection signal PC sent by the busbar short-circuit detection module and disconnect the second circuit breaker QF2, thereby disconnecting the current flowing through the power-on buffer resistor R1. The contacts of the contactor KM1 are connected in parallel across the series circuit of the second circuit breaker QF2 and the power-on buffer resistor R1. The contactor KM1 is used to receive the contactor signal CC sent by the busbar short-circuit detection module and disconnect the contacts of the contactor KM1, thereby disconnecting the current of the DC bus. Adding a second circuit breaker QF2 to the circuit of the power-on buffer resistor R1 configured in a conventional inverter ensures that the energy storage filter unit is physically and completely disconnected from the incoming line side when a busbar short circuit occurs. This prevents the incoming line side from continuing to transfer energy to the energy storage filter module through the contactor KM1 or the power-on buffer resistor R1 when a short circuit occurs, protecting the circuit from burning out.

[0040] The control current uses a single-chip microcomputer as the control chip. The single-chip microcomputer has an operating time of 1 to 10 microseconds, and the operating time of the second circuit breaker QF2 and the contactor KM1 is 1 to 10 milliseconds. The response time to the short-circuit state is very short, ensuring that the short-circuit accident will not escalate and there will be no large-scale burn marks at the short-circuit point. After the second circuit breaker QF2 and the contactor KM1 are disconnected, the power-on buffer module is completely disconnected from the subsequent energy storage filter module and the user's input side. No energy is output from the input side to the energy storage filter module, ensuring the safety of the energy storage filter module and the inverter module. At the same time, there is no energy flowing in the rectifier module, so the rectifier module is also safe. Therefore, this embodiment ensures the safety of the entire inverter and solves the problem that in conventional inverter configurations, if the busbar is short-circuited, the input side will continue to input energy to the DC bus through the power-on buffer resistor R1, causing the series capacitor of the energy storage filter module to ignite and the rectifier module to be damaged.

[0041] See also Figure 2 In Example 2 of the present invention, the structure of the busbar short-circuit detection module and its connection relationship within the inverter are identical to those of Example 1. The shunt tripper KT1 is connected to the incoming line breaker QF1 via a transmission mechanism. The incoming line breaker QF1 includes three switches connected in series to the inverter's three-phase input power lines L1, L2, and L3, respectively, for coordinated on / off switching. The shunt tripper KT1 is used to receive the protection signal PC sent by the busbar short-circuit detection module and disconnect the incoming line breaker QF1, thereby disconnecting the inverter's three-phase input power and ultimately interrupting the current flowing through the inverter's DC bus. The tripping time of the incoming line breaker QF1 in this embodiment is 100 to 200 milliseconds, which is slightly slower than the protection speed of Example 1, but still achieves the purpose of protecting the DC bus. Furthermore, after the incoming line breaker QF1 disconnects the three-phase incoming line power, the secondary control circuit on the user side is de-energized, meeting the requirements for protecting the inverter and user circuits.

[0042] See also Figure 4 , a frequency converter busbar short-circuit protection method, comprising the following steps:

[0043] S1: Preset short-circuit threshold voltage U in the control circuit of the busbar short-circuit detection module S and short-circuit threshold time T S .

[0044] S2: The first sampling circuit M1 detects the first series capacitor C1 to obtain the voltage U C1 , converts it into an analog signal U1 and sends it to the control circuit; the second sampling circuit M2 detects the second series capacitor C2 to obtain the voltage U C2 , converted into an analog signal U2 and sent to the control circuit; the control circuit records the duration T of the voltage.

[0045] S3: The control circuit compares the voltage U1, voltage U2 and the short-circuit voltage threshold U S The value of the short circuit time threshold T and the duration T S The size of the device and the actions according to different connection situations;

[0046] When the shunt release KT1 is connected to the second circuit breaker QF2, the judgment is as follows:

[0047] If U1>U S 、U2>U S , and T>T S , determine that no short circuit occurs, mark the short circuit state as A, and execute step S2;

[0048] If U1<U S 、U2>U S , and T>T S , it is determined that the first series capacitor C1 is short-circuited, the short-circuit state is marked as B, the control circuit sends a protection signal PC to disconnect the shunt release KT1 to disconnect the second circuit breaker QF2, and sends a contactor signal CC to disconnect the contacts of the contactor KM1, and prompts the user that the first series capacitor C1 is short-circuited;

[0049] If U1>U S 、U2<U S , and T>T S , determine that the second series capacitor C2 is short-circuited, mark the short-circuit state as C, and the control circuit sends a protection signal PC to disconnect the shunt release KT1 to disconnect the second circuit breaker QF2, and sends a contactor signal CC to disconnect the contacts of the contactor KM1, and prompt the user that the second series capacitor C2 is short-circuited;

[0050] If U1<U S 、U2<U S , and T>T S , it is determined that the busbar is directly short-circuited, and the short-circuit state is marked as D. The control circuit sends a protection signal PC to disconnect the shunt release KT1 and the second circuit breaker QF2, and sends a contactor signal CC to disconnect the contact of the contactor KM1, and prompts the user that the busbar is short-circuited;

[0051] When the shunt release KT1 is connected to the incoming circuit breaker QF1, the judgment is as follows:

[0052] If U1>U S 、U2>U S , and T>T S , determine that no short circuit occurs, mark the short circuit state as A, and execute step S2;

[0053] If U1<U S 、U2>U S , and T>TS , it is determined that the first series capacitor C1 is short-circuited, the short-circuit state is marked as B, the control circuit sends a protection signal PC to disconnect the shunt release KT1 and disconnect the incoming circuit breaker QF1, and prompt the user that the first series capacitor C1 is short-circuited;

[0054] If U1>U S 、U2<U S , and T>T S , it is determined that the second series capacitor C2 is short-circuited, the short-circuit state is marked as C, the control circuit sends a protection signal PC to disconnect the shunt release KT1 and disconnect the incoming circuit breaker QF1, and prompt the user that the second series capacitor C2 is short-circuited;

[0055] If U1<U S 、U2<U S , and T>T S , it is determined that the busbar is directly short-circuited, the short-circuit state is marked as D, the control circuit sends a protection signal PC to disconnect the shunt release KT1 and disconnect the incoming circuit breaker QF1, and prompt the user that the busbar is short-circuited.

[0056] S4: The control circuit determines whether the short-circuit fault is eliminated; if the short-circuit fault is not eliminated, the disconnect signal is continuously issued, so that the circuit breaker will be disconnected again when the user manually closes the circuit breaker and powers on; if the short-circuit fault is eliminated, the disconnect signal is stopped, and the inverter can operate normally after the user manually closes the circuit breaker and powers on, and step S2 is executed.

[0057] The above embodiments are intended only to illustrate the design concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. The scope of protection of the present invention is not limited to the above embodiments. Therefore, any equivalent changes or modifications made based on the principles and design concepts disclosed in the present invention are within the scope of protection of the present invention.

Claims

1. A frequency converter busbar short-circuit protection device, characterized in that: The invention comprises a busbar short circuit detection module, a shunt release and a circuit breaker arranged in the frequency converter; the frequency converter comprises a rectifier module, a power-on buffer module, an energy storage filter module and an inverter module connected in series in sequence, the busbar short circuit detection module is connected in parallel between the positive and negative ends of the DC bus of the energy storage filter module through the detection input end, and is used to detect the voltage between the positive and negative ends of the DC bus and determine whether a short circuit occurs; the busbar short circuit detection module is connected to the signal input of the shunt release KT1 and the contactor KM1 of the power-on buffer module through the signal output end. The shunt release KT1 is connected to the circuit breaker through a transmission mechanism and is used to disconnect the circuit breaker when receiving the disconnect signal. The circuit breaker includes an incoming circuit breaker QF1 and a second circuit breaker QF2, or the circuit breaker includes an incoming circuit breaker QF1. The contacts of the incoming circuit breaker QF1 are connected in series to the incoming three-phase AC power main circuit of the inverter, and the contacts of the second circuit breaker QF2 are connected in series to the DC bus circuit of the inverter, and are used to disconnect the current flowing through the DC bus of the inverter by disconnecting the circuit breaker contacts. A buffer resistor R1 is connected in series to the positive terminal of the DC bus of the inverter's power-on buffer module. A contactor KM1 is connected in parallel across the power-on buffer resistor R1, and is configured to close contacts to bypass the power-on buffer resistor R1 when power-on charging is complete, and to open contacts upon receiving a disconnect signal, thereby disconnecting the current flowing through the inverter's DC bus. The bus short-circuit detection module includes a first sampling circuit M1, a second sampling circuit M2, and a control circuit. The detection input terminals of the first sampling circuit M1 and the second sampling circuit M2 are respectively connected in parallel across the first series capacitor C1 and the second series capacitor C2 of the inverter's energy storage filter module. The signal output terminals of the first sampling circuit M1 and the second sampling circuit M2 are respectively connected to the signal input terminal of the control circuit, and are configured to sample the voltage across the energy storage filter capacitor, convert it into a low-voltage analog signal, and transmit it to the control circuit. The control circuit is configured to preset a short-circuit threshold voltage and short-circuit threshold time, record the voltage duration, and determine the short-circuit state and transmit a disconnect signal by comparing the voltage with the short-circuit voltage threshold value and the duration with the short-circuit time threshold.

2. The inverter busbar short-circuit protection device according to claim 1, characterized in that: The second circuit breaker QF2 and the power-on buffer resistor R1 are connected in series in sequence to the positive end of the DC bus of the inverter's power-on buffer module. The shunt release KT1 is connected to the second circuit breaker QF2 through a transmission mechanism and is configured to receive the protection signal PC sent by the busbar short-circuit detection module and disconnect the second circuit breaker QF2, thereby interrupting the current flowing through the power-on buffer resistor R1. The contacts of the contactor KM1 are connected in parallel across the series circuit of the second circuit breaker QF2 and the power-on buffer resistor R1. The contactor KM1 is configured to receive the contactor signal CC sent by the busbar short-circuit detection module and disconnect the contacts of the contactor KM1.

3. The inverter busbar short-circuit protection device according to claim 1, characterized in that: The incoming circuit breaker QF1 includes three switches that are connected in series on the three-phase input power lines L1, L2, and L3 of the inverter, and are linked to each other for on and off. The shunt release KT1 is connected to the incoming circuit breaker QF1 through a transmission mechanism. The shunt release KT1 is used to receive the protection signal PC sent by the bus short-circuit detection module, disconnect the incoming circuit breaker QF1, thereby disconnecting the three-phase input power of the inverter, and finally disconnecting the current flowing through the DC bus of the inverter.

4. A protection method for a frequency converter busbar short-circuit protection device according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: Preset short-circuit threshold voltage U in the control circuit of the busbar short-circuit detection module S and short-circuit threshold time T S ; S2: The first sampling circuit M1 detects the first series capacitor C1 to obtain the voltage U C1 , converted into analog signal U1 and sent to the control circuit; The second sampling circuit M2 detects the second series capacitor C2 to obtain the voltage U C2 , converts it into an analog signal U2 and sends it to the control circuit; the control circuit records the duration T of the voltage; S3: The control circuit compares the voltage U1, voltage U2 and the short-circuit voltage threshold U S The value of the short circuit time threshold T and the duration T S The size of the sensor determines whether a short circuit occurs. If no short circuit occurs, step S2 is executed. If a short circuit occurs, a disconnection signal is sent to enable the protection device to complete the corresponding action and step S4 is executed. S4: The control circuit determines whether the short-circuit fault is eliminated; if the short-circuit fault is not eliminated, the disconnection signal is continuously issued; if the short-circuit fault is eliminated, the disconnection signal is stopped and step S2 is executed.

5. The protection method according to claim 4, characterized in that: If the shunt release KT1 is connected to the second circuit breaker QF2, the specific steps in step S3 are as follows: The control circuit compares the voltage U1, voltage U2 and the short-circuit voltage threshold U S The value of the short circuit time threshold T and the duration T S Size: If U1>U S 、U2>U S , and T>T S , determine that no short circuit occurs, mark the short circuit state as A, and execute step S2; If U1<U S 、U2>U S , and T>T S , it is determined that the first series capacitor C1 is short-circuited, the short-circuit state is marked as B, the control circuit sends a protection signal PC to disconnect the shunt release KT1 to disconnect the second circuit breaker QF2, and sends a contactor signal CC to disconnect the contacts of the contactor KM1, and prompts the user that the first series capacitor C1 is short-circuited; If U1>U S 、U2<U S , and T>T S , determine that the second series capacitor C2 is short-circuited, mark the short-circuit state as C, and the control circuit sends a protection signal PC to disconnect the shunt release KT1 to disconnect the second circuit breaker QF2, and sends a contactor signal CC to disconnect the contacts of the contactor KM1, and prompt the user that the second series capacitor C2 is short-circuited; If U1<U S 、U2<U S , and T>T S , it is determined that the busbar is directly short-circuited, and the short-circuit state is marked as D. The control circuit sends a protection signal PC to disconnect the shunt release KT1 and disconnect the second circuit breaker QF2, and sends a contactor signal CC to disconnect the contacts of the contactor KM1, and prompts the user that the busbar is short-circuited.

6. The protection method according to claim 4, characterized in that: If the shunt release KT1 is connected to the incoming circuit breaker QF1, the specific steps in step S3 are as follows: The control circuit compares the voltage U1, voltage U2 and the short-circuit voltage threshold U S The value of the short circuit time threshold T and the duration T S Size: If U1>U S 、U2>U S , and T>T S , determine that no short circuit occurs, mark the short circuit state as A, and execute step S2; If U1<U S 、U2>U S , and T>T S , it is determined that the first series capacitor C1 is short-circuited, the short-circuit state is marked as B, the control circuit sends a protection signal PC to disconnect the shunt release KT1 and disconnect the incoming circuit breaker QF1, and prompt the user that the first series capacitor C1 is short-circuited; If U1>U S 、U2<U S , and T>T S , it is determined that the second series capacitor C2 is short-circuited, the short-circuit state is marked as C, the control circuit sends a protection signal PC to disconnect the shunt release KT1 and disconnect the incoming circuit breaker QF1, and prompt the user that the second series capacitor C2 is short-circuited; If U1<U S 、U2<U S , and T>T S , it is determined that the busbar is directly short-circuited, the short-circuit state is marked as D, the control circuit sends a protection signal PC to disconnect the shunt release KT1 and disconnect the incoming circuit breaker QF1, and prompt the user that the busbar is short-circuited.

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